1. Field of the Invention
This invention relates to improvements in or relating to an antenna for use with a small communication equipment such as a portable radio equipment, and more particularly to an antenna for a radio equipment which can eliminate a disadvantage that an end portion of the antenna element is liable to be deformed and damaged or broken by an impact when it drops or in a like accident, because an end portion of an antenna element which can be retracted into the radio equipment is extended from a body of the radio equipment at an antenna accommodated portion.
2. Description of the Related Art
Recently, portable radio equipment which are small in size and light in weight and superior in portability have been widely available. An example of an antenna for use with such portable radio equipment is disclosed in and known from Japanese Patent Laid-Open Application No. Heisei 7-38315. The antenna is shown in FIGS. 1 and 2.
FIG. 1 is a sectional view showing the antenna in a condition in which it is extended from a housing, and FIG. 2 is a sectional view showing the antenna in another condition in which it is retracted in the housing. Referring to FIGS. 1 and 2, reference numeral 1 denotes a housing of the portable radio equipment, and reference numeral 2 denotes an antenna mounted for extending and retracting movement relative to the housing 1. Antenna 2 includes a first coil case 3 provided at an end thereof, and linear antenna element 4 connected to first coil case 3. Coiled antenna element 5 is provided in the inside of first coil case 3 and electrically connected to linear antenna element 4. Large diameter portions 4a and 4b are formed at the upper and lower ends of linear antenna element 4, and connecting end portion 4c is formed at the lower end of linear antenna element 4.
Reference numeral 6 denotes a connecting metal element embedded in housing 1. Whether antenna 2 is in the condition extended from or retracted in housing 1 as shown in FIGS. 1 and 2, respectively, connecting metal element 6 is electrically connected to large diameter portions 4a and 4b of linear antenna element 4. Further, connecting metal element 6 is connected to circuit board 8 by way of feed line 7 and connected to a radio circuit by way of matching circuit 9.
Reference numeral 10 denotes a second coil case. Second coil case 10 is constituted from a connecting terminal 11 which is electrically connected to the connecting end portion 4c of linear antenna element 4 when antenna 2 is retracted in housing 1, and coiled antenna element 12 connected to connecting the terminal 11. The other end of the coiled antenna element 12 is grounded to a grounding plate of circuit board 8 by way of feed line 13.
However, when antenna 2 described above is retracted as shown in FIG. 2, since the first coil case 3 extends outwardly of the radio equipment while first coil case 3 and linear antenna element 4 are coupled rigidly to each other, when an impact acts upon first coil case 3 because of a drop of the radio equipment or collision with an obstacle or by some other cause, large diameter portion 4a of linear antenna element 4 directly below first coil case 3 is liable to be deformed and damaged or broken, making a cause of failure.
In a radio equipment which includes an antenna of the conventional structure described above, in order to prevent possible damage to or a break of the end portion of the antenna by an external stress, first coil case 3 must be minimized so as to minimize the extending amount of first coil case 3 when the antenna is retracted. This, however, results in reduction in dimension of coiled antenna element 5 of first coil case 3 and consequently in degradation of the sensitivity characteristic of the antenna in its retracted condition.